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Discussion Starter #1
Hi,

I rebuilt my 2L box about 6K miles ago and it's been great. However, since starting to race my car recently I noticed it's been progressively getting harder to change gears. Today, I was constantly grinding 3rd and 4th and couldn't get it in reverse to back into the garage.

The throw on the lever seems good (1.5 inches?) and the friction plate, throw-out bearing, and flywheel (lightweight) are new.

Any ideas? Before I race tomorrow I think I'll drain the tranny and refill it.

Thanks.
 

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Clutch is where I would start looking. Racing is hard on clutches ...

Also have you replaced your hydraulic clutch hose from the master cylinder to the slave?, as my father had a hose collapse internally with his BMW 2002tii that caused clutch problems.
Pete
 

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I was with RJ when the friction material separated from the disk and eventually prevented the clutch from releasing. He posted about it.
 

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Discussion Starter #4
Hi,

Tough weekend (sort of) racing. I couldn't run today and only got one session in yesterday.

Here's the symptoms:

- Racing at Thompson last couple of times I would crunch 4th gear coming onto the straight. Every other gear change was fine.
- This weekend at Palmer (really cool track) I found that I couldn't downshift into third easily and eventually couldn't downshift into fourth.
- Coming into the paddock I couldn't even get it in reverse without a lot of coaxing by touching other gears.

What we did:

- Verified that the slave was working and the fork was traveling (about an inch)
- We found that the locking nut on the clutch pushrod off the armature (going into the clutch master) backed off the fork by about 1/4 inch. Assuming that the pushrod migrated as well, we measured the distance to the pin and found it to be 114 mm (spec is I think 134).
- We also found the clutch pedal was just a little lower than the brake pedal (1 inch), so we lifted it up as we extended the pushrod out to about 120 mm (4.75 inches) thinking that this would provide more travel into the MC.
- Raced and had the same issues
- We bled the system (twice) and wound up with no clutch disengagement at all

Observations:

- After bleeding (done properly), the pedal seemed soft and I found I was able to lift the pedal up about 2 inches to the point that it was higher than the brake pedal. This felt like the pin was moving on the shaft.
- inspected the pedal arm as best I could and could not find any breaks/cracks
- noticed that when the clutch pedal is pushed, the hose to the slave moves/twists (ordered a ss braided hose to replace)

Plan:

- Replace clutch hose with braided hose. Move to MC or SC replacement if no improvement.
- Attempt to tighten clutch pedal attachment to pivot or replace?

Couldn't race obviously which was disappointing since it's a really nice track, lots of great cars, and really nice people (VRG).

Advice appreciated!

Michael.
 

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When you did work on your transmission, did you also replace the clutch pressure plate and disc with a new Sachs pressure plate and disc? If you did that may be your problem. We've found that the new, made-in-China Sachs pressure plates are quite marginal and won't stand up to racing or even hard driving the way the old oem Sachs pressure plates would. Paul Spruell sells an uprated pressure plate as do some other vendors. You can also convert to a early 911S (1967) pressure plate which is costly but more robust. When we built my 2 liter hot-rod engine for my Super my friend Bob Fernald found a used but perfectly good 1986 pressure plate to use because, as he siad, "pressure plates rarely go bad". It's working quite well.
 

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I have had similar symptoms with broken Marcel (wafer) spring in the clutch driven (friction) plate ... generally a driven plate without Marcel springs is preferable for HD use anyway.
 

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Discussion Starter #7
Just following up... My pressure plate actually broke where it screws into the flywheel. Not sure if it was flawed or possibly not secured properly, but the flange where it screws to the flywheel had oblong holes from stress and one screw was backed out and the metal actually split at that point. The slight twist in the pressure plate was enough to prevent disengagement.
 

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Interesting and timely. I'm replacing all the bolts in my flywheel to crank and PP to flywheel for this reason. Going to use loctite red on the flywheel, blue on the PP.

Did the dowels also fail?
 

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Discussion Starter #11
Actually, I had multiple problems at the same time making it difficult to troubleshoot. After replacing the pressure plate and getting everything back together, we were bleeding the system and the clutch pivot arm gave out. I welded it and put it back in while waiting for a new one from John Kortak... just put that one in Saturday.

The clutch works fine, but there's a loud whistling sound when depressed and I'm concerned something isn't right. The pressure plate I bought was a "high performance" one from Spruell along with a Tilton-type throw-out bearing.
 

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Interesting and timely. I'm replacing all the bolts in my flywheel to crank and PP to flywheel for this reason.
Those are special flywheel bolts. Not just dimensions, tensile strength, hardness but also thead pattern. The roots and crests of the threads are rounded to enhance fatigue resistance - similar to UNR. Make sure that the ones you use are at least OEM standard
 

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Richard Jemison
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Clutch issues

First determine if your clutch MC lever at the enf of the clutch rod is securely welded. That`s a typical failure point If you can pull the clutch petal up with the release arm back against the firewall, it is broken. Easy fiv is to grind away (or cut the top of the lever off exposing a part of the rod) These are only welded at the butt of the rod and if you weld the exposed rod to the lever it will be far stronger and last.

If that doesn`t result in normal release, then the clutch disk is separated locking itself to the flywheel.

Stock disk are unsuitable to racing. You need a no spring disk with organic material bonded AND riveted to the metal plate. If riveted only expect failure.

Stock PPs use 3 bands locating the contact plate yo the cover,. Any reverse load can collapse them as they are designed to only take load in a pull direction (as in acceleration). Ant shatp load gearing down or in a spin will damage the PP.

Racing seriously requires race clutch assemblies IE Tilton, Quartermaster, etc.
 
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